Introduction

It was mid-July 1979 in Belgium when BMW unveiled the 635 CSI. In a return to their tradition of producing performance-cum-luxury machines, the 635 CSI was powered by what was virtually a tamed version of the 3.5 litre competition engine. BMW were very keen to point out the gutsy in-line 'six' was not an enlarged 3.3-litre motor (as in the 633 CSi, and 7-series saloons) but was a detuned version of the motor which was fitted to the mid-engined M1 Coupe.

The M88 Engine

The M88 engine (the M1's motor was designated M90) developed 160 kW at 5200 rpm - nine per cent more power than the 3.3-litre 633CSi unit, but at 5200 instead of 5500 rpm. The bigger, injected-engine was turbine-smooth, amazingly responsive, and powerful enough to give the 635 CSi a top speed of more than 218 km/h, as well as a 0-100 km/h acceleration figure of 7.5 seconds.

The revised suspension transformed the handling of the 635 CSI. There were some detractors who believed BMW were trying to drop their performance image when the Munich firm introduced the 630 CS and 633 CSi models, but these people were forced to eat their words when got behind the wheel of the CSI. The performance may not seem so startling by today’s standards, but it was bloody good for 1979.

BMW's thinking was dead right - they were keen to sell the new coupe body to discerning motorists who didn't necessarily want a sports car, and the earlier cars undoubtedly attracted plenty of buyers who wouldn't have bought the fierce old-style coupe, but liked the looks, sophistication of the new-style model.

Thankfully the suspension was also very good too. It was so well sorted that BMW even made the 635’s suspension package available as an optional fitment to the 630 CS and 633 CSi at a cost of DM200 (about $85) for those owners who wanted to corner faster and handle better. The 635 was recognisable by the deep front air-dam, and the 'rubber' boot-lid spoiler. At launch the CSI was fitted with superb leather-trimmed Recaro seats, but production models were made available with BMW seats.

The Gertag Gearbox

The engine was mated to a five-speed Getrag gearbox, no automatic transmission being available. And in a strange move, BMW decided that the car should remain as a "European" high-performance car, not to be choked by emission legislation, and therefore not to be exported to the USA. The Getrag gearbox had a good spread of gear ratios, but there was some criticism of the change itself on the first models produced. BMW were listening, and set about improving it. The central lever had a spring bias to the centre of the 'gate', and because of it, there could be confusion whan cog-swapping. The change pattern was similar to Porsche from the era, with first engaged with a left-and-back movement, the other four speeds being obtained through the normal H-pattern.

Motor testers noted that first gear engagement could be stiff and notchy, and was obviously intended to be so that it couldn’t be selected at speed. The other four were fair enough, except, with that spring bias it was possible to get second when you want fourth. The whole gear-change procedure was a little 'rubbery'. Small gearbox criticisms aside, the enormous power and torque of the ohc 'six', the responsiveness, and the fantastic handling made the 635 CSi a real delight to drive. There were few cars that were its equal.

Right-hand drive models left the factory in late 1979 with coupe production (all models) being around 6000 per year. The introductory price in Germany was DM50.000 ($21,391 approx), and BMW regarded the car as a bargain. Again, they were right.The successor of 3.0CS coupe was born as 630CSi first,
then with engine displacement diversified to 2.8, 3.3
(exclusively for the US market) and then 3.5 litres.